Kinetics of the Dissociation of Weak Acids and Bases—Application of Polarography and Voltammetry at Constant Current

Delahay, Paul; Vielstich, W.

doi:10.1021/ja01624a002

Cited by 44 publications

(12 citation statements)

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“…These values were one order smaller than those reported previously. [4][5][6] The origin of the discrepancy between the results of the present study and those of the previous ones is not clear, although the present study was theoretically self-consistent in terms of RDE and SHM. The dissociation rate, k f , and the recombination rate, k b , calculated for CH 3 COOH and C 2 H 5 COOH were a few times higher than that reported in the previous study [4][5][6] and that of the diffusion-controlled second-order reaction.…”

Section: Resultscontrasting

confidence: 99%

“…In addition, several steps in the approximation to deduce the theoretical relation constitute another source of inconsistency among the various studies. Thus, a significant difference in k f and k b of this study and previous studies [5][6][7][8][9] was inevitable. Firstly, (K/k f ) 1/2 (Table IV) was calculated from the experimental slope and eqns.…”

Section: Resultsmentioning

confidence: 64%

“…The reaction current that could not be detected in the ordinary current-potential curve was readily apparent using SHM. The prospective application of SHM to the fast electrode reaction was also suggested; it is the subject of an ensuring study on the hydrogen evolution reaction of a strong acid and Fe(CN) 6 4− /Fe(CN) 6 3− . The data also suggested that SHM should be used in addition to RDE for analysis of the electrode reaction based on the Koutecky-Levich equation.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Dissociation Rates of Weak Acids Using Sinusoidal Hydrodynamic Modulated Rotating Disk Electrode Employing Koutecky-Levich Equation

Kanzaki

Tokuda

Bruckenstein

2014

J. Electrochem. Soc.

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The hydrogen evolution reaction of HCOOH, CH 3 COOH, and C 2 H 5 COOH solutions consists of two different reduction processes depending on the evaluated potential region; (1) independent reduction of RCOOH and (2) simultaneous reduction of RCOOH and H 2 O. The reduction of each carboxylic acid generates an apparent convective diffusion-controlled limiting current. The first achievement of the present study is that by using a rotating disk electrode (RDE) and a sinusoidal hydrodynamic modulated-rotating disk electrode (SHM), it was elucidated that the additive property of the reduction currents of RCOOH and H 2 O was not effective, and the convective-diffusion current was successfully distinguished from the total current. The second achievement is the successful analysis of the rotation-speed dependency of the limiting current in RDE and SHM using a modified theory of the Koutecky-Levich equation. The slopes of the plots for each carboxylic acid increased in the following sequence: RDE, SHM (p = 0.05), and SHM (p = 0.24), which is consistent with the theory. The dissociation rates of the carboxylic acids and the reverse recombination rate were calculated. The dissociation rates of various carboxylic acids have previously been determined by applying the modified Koutecky-Levich relation 1 based on the rotational-speed dependency of the limiting current for H + reduction at the rotating disk electrode (RDE). [2][3][4] The dissociation rates determined in the previous study 4 were apparently consistent with the results obtained using other methods.5-9 However, we now raise an elementary question about the procedure used for determining the H + -reduction limiting current, which is the basis of the Koutecky-Levich analysis. Based on sinusoidal hydrodynamic modulation (SHM) study, [10][11][12][13][14] we conclude that the potential-dependent limiting current associated with H + -reduction in dilute acid solutions contains a significant potential-dependent current associated with OH − generated simultaneously from the supporting electrolyte. The present SHM analysis of dilute HCl solution and an uncharged weak acid solution, such as formic, acetic, or propionic acid solutions, clearly demonstrates a pure convective diffusion-controlled potential region in addition to that associated with OH − . It is demonstrated that the "limiting" H + -reduction current for formic, acetic, and propionic acids varies considerably with the potential, and pure convective diffusion-controlled potential region could not be determined from the RDE data. Thus, it is likely that the previous studies by other researchers based on RDE 2-4 have somewhat dealt with this issue. This fundamental issue exists for both RDE and SHM data. The present approach for determining the acid dissociation rates requires appropriate choice of an electrode potential that excludes the effect of OH − in the convective diffusion-layer. In this study, we also derive a linear approximation of SHM as well as the RDE theory for determining the rate of dissociation of a...

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Section: Resultscontrasting

confidence: 99%

Section: Resultsmentioning

confidence: 64%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Dissociation Rates of Weak Acids Using Sinusoidal Hydrodynamic Modulated Rotating Disk Electrode Employing Koutecky-Levich Equation

Kanzaki

Tokuda

Bruckenstein

2014

J. Electrochem. Soc.

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“…This is easily rationalized: removal of the 250 ionized portion of a sample results in further ionization of the unionized portion for equilibrium to be 251 maintained. Formic and acetic acids showed dissociation half-lives of 13 and 2.4 s, respectively [25], 252 compared to the 11 s residence time. While pH does not directly affect the dissociation rate, the lower transfer 253 efficiency at pH < 2.5 is caused, at least in part, by the preferential transport of high mobility anions that were 254 used to adjust the pH.…”

Section: Sample Ph Effects On the Present Methods And On Solid Phase Ementioning

confidence: 98%

On-line electrodialytic matrix isolation for chromatographic determination of organic acids in wine

Ohira

Kuhara

Shigetomi

et al. 2014

Journal of Chromatography A

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Chromatographic determination of organic acids is widely performed, but the matrix often calls for lengthy and elaborate sample preparation prior to actual analysis. Matrix components, e.g., proteins, non-ionics, lipids etc. are typically removed by a combination of centrifugation/filtration and solid phase extraction (SPE) that may include the use of ion-exchange media. Here we report the quantitative electrodialytic transfer of organic acids from complex samples to ultrapure water in seconds using cellulose membranes modified with N,N-dimethylaminoethyl methacrylate, which essentially eliminates the negative ζ-potential of a regenerated cellulose membrane surface. The transfer characteristics of the ion transfer device (ITD) were evaluated with linear carboxylic acids. While the ion transfer efficiencies may be affected by the acid dissociation constants, in most cases it is possible to achieve quantitative transfer under optimized device residence time (solution flow rate) and the applied voltage. In addition, the transfer efficiency was unaffected by the wide natural variation of pH represented in real samples. The approach was applied to organic acids in various samples, including red wine, considered to represent an especially difficult matrix. While quantitative transfer of the organic acids (as judged by agreement with standard pretreatment procedures involving SPE) was achieved, transfer of other matrix components was <5%. The processed samples could then be chromatographically analyzed in a straightforward manner. We used ion exclusion chromatography with direct UV detection; in treated samples; there was a dramatic reduction of the large early peaks observed compared to only 0.45μm membrane filtered samples.

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“…However in LSV, the voltage is scanned from a lower limit to an upper limit as shown above 61 . CV is an electrochemical technique which measures the current that develops in an electrochemical cell during charge and discharge processes 62,63 . It could be performed by varying the potential between a working electrode and a reference electrode while measuring the resulting current between the working and counter electrodes.…”

Section: Fig 5 Linear Sweep Voltammogrammentioning

confidence: 99%

Solid polymer electrolytes as a prospective class of electrolytes

2021

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Kinetics of the Dissociation of Weak Acids and Bases—Application of Polarography and Voltammetry at Constant Current

Cited by 44 publications

References 1 publication

Dissociation Rates of Weak Acids Using Sinusoidal Hydrodynamic Modulated Rotating Disk Electrode Employing Koutecky-Levich Equation

Dissociation Rates of Weak Acids Using Sinusoidal Hydrodynamic Modulated Rotating Disk Electrode Employing Koutecky-Levich Equation

On-line electrodialytic matrix isolation for chromatographic determination of organic acids in wine

Solid polymer electrolytes as a prospective class of electrolytes

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